The product of S gene will be identified as a specific protein band after SDS gel electrophoresis in two ways. In one UV irradiated cells will be infected separately with lambda R and lambda RS phage in the presence of C14 amino acids. The inner membrane fraction will be isolated from each lot of infected cells, solubilized and fractionated by SDS polyacrylamide gel electrophoresis. The S product should be missing or have a lower molecular weight in the lambda RS infected membrane. The other approach will be to clone the S gene using a plasmid containing the lac promoter operator region so that S product synthesis can be induced with I PTG. The inner membrane will be isolated from induced and uninduced cells, labelled with C14 amino acids, solubilized in SDS, fractionated by SDS gel electrophoress to look for a protein whose synthesis is increased in the induced cells. Once the protein is identified it will be incorporated into phospholipid vesicles to determine its effect on the permeability of vesicles. In addition, studies of the regulation of the synthesis and activity of the S protein will be carried out in whole cells.